Spirited heroines and sardonic heroes populate this sexy Regency-era thriller by the ever reliable Quick, alter ego of Jayne Ann Krentz. This time out, Quick offers the parry and thrust of danger and romance, as embodied in resourceful Lavinia Lake and roguish Tobias March. Lavinia first encounters Tobias when he bursts into her antiques shop in Rome, trashing her wares, all the while claiming to be on the trail of a murderer and warning Lavinia that she is in danger. There's also talk of treason, a criminal organization known as the Blue Chamber and an evil mastermind named Azure. Despite her skepticism, Lavinia returns with her niece, Emeline, to London, where she is caught up in more intrigue. She sets herself up as a private detective and even though stubbornness on both sides leads to an oil-and-water pairing, she soon finds herself in business with Tobias, attempting to foil a blackmail scheme, locate the culprit in a series of murders and identify the surviving member of Azure's organization. Arch humor and the expert removal of bodices are Quick's stock in trade, and the old formula still works splendidly. As usual, the novel's outcome is visible a mile off, but familiarity, after all, is golden in literary franchise land. Major ad/promo. (Apr. 10)